Field of the Invention
The present invention relates to a process, a device and an apparatus for the production of a honeycomb body having a plurality of at least partially structured metal sheets which form a plurality of passages through which a fluid can pass.
Catalytic converters are used for reducing the emission of pollutants from internal combustion engine, in particular Otto engines. The catalytic converter has a catalytically active substance which disposed on a carrier. In order to provide the largest possible surface area for the catalytically active substance, the carrier body may have a honeycomb form. Such a honeycomb body is formed from one or more stacks of a plurality of at least partially structured sheets. U.S. Pat. No. 4,923,109 discloses a design configuration of a honeycomb body in which the stack is twisted or wound in opposite directions about itself and about a central region.
International publication WO 90/03220 describes a metallic catalyst carrier body. That carrier body is made up from at least partially structured sheets. It includes three or more stacks of sheets which are folded about a bend line in the central region of the honeycomb body and twisted in opposite directions around each other and around the central region with the bend lines.
Further catalyst carrier body configurations are disclosed, for instance, in international publication WO 94/01661.
Catalyst carrier bodies of that kind are produced with apparatuses that include a forked winding or wrapping device which rotates about a central axis and which engages each stack. A shaping mold or matrix has an internal contour which substantially corresponds to the external contour of the honeycomb body in the wound condition.
German published, non-prosecuted application DE 195 22 327 A1 discloses an apparatus for the production of a honeycomb body that has a plurality of at least partially structured sheets forming a plurality of passages through which a fluid can pass. The apparatus includes a forked wrapping or winding device which is rotatable about a central axis and which engages each stack, and a shaping mold or matrix which is of an internal contour corresponding to the external contour of the honeycomb body to be produced. The mold or matrix surrounds the winding device. The wall of the mold is formed with at least one opening for the stack ends. The opening extends substantially parallel to the central axis. During the production of a honeycomb body, at least one stack which is formed by a multiplicity of at least partially structured sheets is introduced into the mold, with the ends of each stack projecting out of the mold through openings. Each stack is held in a central region by a winding device which is rotatable about a central axis. As the winding device rotates, the stacks are twisted to form a honeycomb body which fills the entire mold.
German published, non-prosecuted application DE 195 21 685 A1 also discloses an apparatus and a process for the production of a honeycomb body. The apparatus includes a forked winding device which is rotatable about an axis and which engages each stack, and mold segments which close to define a mold. The mold is formed from at least two mold segments. Each mold segment is pivotable about a pivot axis which respectively extends parallel to the axis of the winding device, opposite to the direction of rotation of the winding device. The mold segments are closed in opposite relationship to the direction of rotation of the winding device when the stack has reached a predetermined degree of winding.
The wound honeycomb bodies are conventionally introduced into tubular casings. The honeycomb bodies are introduced into a tubular casing substantially immediately following the winding operation. In that procedure, the honeycomb body is pressed into the tubular casing in the axial direction thereof.
The carrier body which is produced in that way is subjected to further production steps which involve for example brazing, sintering or welding. The metal honeycomb bodies are integrated into an exhaust system. For that purpose the two ends of the carrier body are connected to a respective pipe of the exhaust system. To provide for a satisfactory connection between the tubular casing of the carrier body and the component parts of the exhaust system, it is necessary for the dimensions of the tubular casing and the contour thereof to be within certain tolerances. In order to observe the required tolerances, the art calibrates the tubular casing of the carrier body prior to and/or after the insertion of the honeycomb body. The calibration is generally effected in such a way that a tool with a plurality of segments is introduced into the tubular casing and the individual segments are spread radially outwardly. The segments are spread beyond the yield limit of the casing material so that the tubular casing is stress-free in that region. International application WO 96/14500 discloses an apparatus with which it is possible to calibrate a honeycomb body with a tubular casing.
Moreover, international application WO 96/12876 discloses a catalyst carrier body in which the free flow cross-section of the passages is closed in an outer annular region, at least in a portion of the exhaust gas flow. The passages are closed by plastic deformation of the passage walls. The closed passages serve to provide for heat insulation.
The winding device with at least one holding mandrel or bar forms a channel in the honeycomb body (e.g. the catalyst carrier body) whose cross-section is substantially determined by the cross-section of the mandrel. When a winding device with a plurality of mandrels is used, there result a corresponding number of such passages within the honeycomb body. The free cross-section of the mandrel passage is usually larger than the cross-section of the other passages in the honeycomb body. The flow profile is affected by the presence of at least one mandrel passage. If the honeycomb body has a plurality of mandrel passages, they have a greater influence on the catalytic effect of the honeycomb body used as a catalyst carrier body.